Touch probes are commonly used to investigate the properties of machined components. A known method of calibrating such probes for measurements is to mount a block of material with one or more bored holes to a measurement table associated with a mechanical holding arm and the touch probe. The hole diameter and hole depth may vary between the holes in order to provide a range of calibration features. Depth and diameter measurements of the holes may be first measured manually with a calipers to provide reference demensions for the touch probe.
When using a touch probe to investigate a component, the touch probe is supported by the mechanical holding arm, allowing measurements to be taken at various points on the surface of the component. The position of the holding arm can be controlled using appropriate software, and the arm may be indexed to various positions within a three dimensional coordinate space, including a nominal origin of that space. The same mechanical arm is typically used to support several different probes during examination of a single component. For example, a touch probe may be used in conjunction with an ultrasonic thickness probe in order to map a component.
To calibrate the touch probe, the touch probe is used to measure the depth and or diameter of the holes. The measured depths and or diameters values are then compared to established reference demensions, obtained using a different method, such as a calipers, in order to calibrate the touch probe. Calibration using the block with bored holes may be repeated using any number of different probes.
Following the calibration procedure, the block with bored holes is removed from the measurement table and a component to be measured is secured to the measurement table for examination. Using the calibration information various dimensions of the component may be measured using the touch probe supported by the mechanical holding arm.